Downing Street refuses to comment on David Cameron pig head claims

The prime minister's official spokesperson today refused to comment on new claims that David Cameron once inserted his genitals into a dead pig.

A new biography written by Conservative peer Lord Ashcroft and journalist Isabel Oakeshott, reveals allegations that the prime minister once took part in a bizarre univeristy initiation ritual involving a pig's head.

The incident is alleged to have taken place during a meeting of the infamous Piers Gaviston dining society at Oxford university.

The prime minister's official spokesperson today refused to comment on the story, telling reporters at a lobby briefing that "I'm not intending to dignify this book by commenting on it."

The chancellor was also asked about the story during his visit to China. Pushed on the claims, an uncomfortable looking George Osborne replied that: "I haven't seen that book".

The source of the claim is an unnamed MP who claims to have seen photographic evidence of the incident.

The book, currently being serialised in the Daily Mail, also repeats claims about drug-taking by the prime minister. Cameron has previously refused to comment on similar claims about his activities while at university.

Reporters were today on a hunt for the source of the new claims, thought to be a Conservative MP who attended Oxford at the same time as David Cameron.